WASHINGTON (AP)—Just as many expected would happen all along, labor negotiations between the NFL and the players’ union are heading right down to the wire—and possibly beyond.

In the first real indication of what’s been going on behind closed doors, the federal mediator overseeing talks said Thursday the two sides made “some progress” during more than 40 hours spread over seven consecutive days of face-to-face meetings, but “very strong differences remain.”

The league and union will resume mediation Tuesday, less than 72 hours before the old collective bargaining agreement is set to expire. If there’s no new deal in place by the end of next Thursday, the union thinks owners will move to lock out players, threatening the 2011 season. The NFL has said, however, that the deadline could be extended.

George Cohen, director of the Federal Mediation and Conciliation Service, released a statement shortly before noon Thursday, his first public comments since he began working with Commissioner Roger Goodell, NFL Players Association executive director DeMaurice Smith and their negotiating teams last week.

“At bottom, some progress was made,” Cohen said, “but very strong differences remain on the all-important core issues that separate the parties.”

While Cohen did not name those issues, the biggest sticking point all along has been how to divide about $9 billion in annual revenues. Among the other significant topics in negotiations: a rookie wage scale; the owners’ push to expand the regular season from 16 games to 18 while reducing the preseason by two games; and benefits for retired players.

NFLPA executive director DeMaurice Smith and the rest of the union’s negotiating team left the building at about 12:30 p.m., three hours after arriving. The NFL departed afterward.

“Just continue talking, man—that’s what we’re doing,” Indianapolis Colts center Jeff Saturday(notes) said as he got into a car. “I think ownership—everybody — needs to know that we’re all committed to it and committed to getting something done.”

Members of both groups now head to Indianapolis for the NFL’s annual scouting combine for draft prospects; the league briefed general managers, coaches and other team officials for 45 minutes Thursday about what would happen if the CBA does expire, while the union speaks to agents on Friday.

“Basically, it was about where we are, where we hope to get and, in case (a new CBA) doesn’t get there, scenarios that will play out,” Jacksonville Jaguars coach Jack del Rio said after the NFL meeting in Indianapolis. “So we got a little bit of information.”

In other words: He and everyone else must wait to see what happens next week. In addition to the return to mediation in Washington, team owners are scheduled to meet in nearby Chantilly, Va., Wednesday and Thursday.

“During the intervening weekend, the parties have been asked by us to assess their current positions,” Cohen said.

Saturday was one of four active players on the NFLPA’s executive committee present Thursday, joined by Denver Broncos safety Brian Dawkins(notes), and Kansas City Chiefs linebacker Mike Vrabel(notes) and guard Brian Waters(notes). Nine of that committee’s 11 members participated at some point during these seven days of talks; union president Kevin Mawae(notes) and New Orleans Saints quarterback Drew Brees(notes) did not.

No NFL team owners attended the talks in Washington. Cohen asked both parties to keep quiet about the mediation, and union lawyer Richard Berthelsen said Thursday that gag order is still in effect.

All Smith would say as he walked toward the union’s headquarters was: “We’ll see you all next week.”

Seeking to keep a lid on what’s happening in the talks, the NFL sent an e-mail on behalf of Goodell to team owners, presidents, general managers and PR employees Thursday, attaching a copy of Cohen’s statement and saying: “We will have no further comment beyond this release and no club or member of your organization should comment beyond this release.”

After months of infrequent and sometimes contentious talks, the NFL and union have been communicating regularly with Cohen present. The sides went more than two months without any formal bargaining until Feb. 5, the day before the Super Bowl. The sides met again once the next week, then called off a second meeting that had been scheduled for the following day.

The most recent CBA was signed in 2006, but owners exercised an opt-out clause in 2008.

During the mediation—which was voluntary and intended to spur progress— the sides have been talking both in full groups and in smaller subcommittee meetings.

“Our time together has been devoted to establishing an atmosphere conducive to meaningful negotiations and, of course, matters of process and substance,” Cohen said in Thursday’s statement. “I can report that throughout this extensive period the parties engaged in highly focused, constructive dialogue concerning a host of issues covering both economics and player-related conditions.”

Also Thursday, there was a hearing before a U.S. District Court judge in Minneapolis to discuss the NFLPA’s complaint that the league improperly negotiated TV deals. The union has accused the NFL of structuring contracts so owners would be guaranteed money from networks even if there were a lockout in 2011—while not getting the most revenue possible in other seasons, when income would need to be shared with players.